A new mount was added in 8.1, a super secret hidden mount.

https://www.wowhead.com/news=289124/...court-of-stars

It has a unique spell effect.
Joined Hivemind150 yd range
Instant
Joins with the target, a member of your Hivemind, limited to the outdoors, following normal vehicle rules.
and
Effect #3 Apply Aura: Mod Mounted Speed %Value: 10%
Effect #4 Apply Aura: Incerase Mounted Speed % - Stacks
Value: 10%
Wont know for sure until someone actually finds the mount in game, but it looks like it increases mount speed by 10% for everyone thats in the hive. You're looking at 50% increased mount speed for 5 boxing.